Study on structural controled rock stability of large-scale underground caverns

Structure controlled block failure is one of rock mass failures in underground engineering practice. This type of failure occurs typically when excavating large-span cravens in hard rock with relatively shallow depth of overburden. In such circumstance, great attention needs to be paid to the spatial distribution and the rock mechanics properties of geological structure in both engineering investigation and stability study of underground openings. On the base of previous studies of failure modes of underground openings under various conditions, the paper focus on the problem nature of large-span underground caverns in hard rock at relatively shallow depth, as well as the requirement of numerical analysis approaches and capabilities. A discontinuum numerical method of distinct element method and software package of 3DEC has been introduced and employed for the stability study of structure-controlled instability problems. It has been found, in terms of the application of this method into caverns, that 3DEC is capable in modelling both the clamping and the opening responses of geological discontinuities under compressive and tensile conditions, respectively. Consequently highly realistic results can be achieved with this approach. In addition, such discontinuum approach has shown its unique advantage in incorporating a large number of discontinuities for stability studies.